Dougal Stanton wrote:
Is there some sort of equivalent of the if/then/else construct for use in the IO monad? For instance the following can get quite tedious:
do bool <- doesFileExist filename if bool then sth else sth'
Is there a more compact way of writing that? Something akin to:
condM (doesFileExist filename) (sth) (sth')
Or maybe there's a more sensible way of doing the above that I've missed. I seem to use endless alternate conditions sometimes and there's bound to be a better way.
Roll your own control structures! Haskell has higher order functions for a reason. This should do the trick (untested): condM condAction thenBranch elseBranch = do bool <- condAction if bool then thenBranch else elseBranch (Hack it into ghci or hugs to find out the type, it's a bit more general than what you need.) Cheers Ben